Heat shield for incandescent lamps



pi. 25, 1945. 1.. A. MCNABB 9 5 HEAT SHIELD FOR INCANDESCENT LAMPS FiledOct. 29, 3.942 2 Sheets-Sheet l [021/5 JfZWYI/QEZ Sam. 25, 39%. L. A. mwfi aa HEAT SHIELD FOR INUANDESGENT LRMPS Filed Oct. 28*, 12942 ma /7/ f9/ 2 f3 5 /02 jag A930 mi /05 63 fzwezz/ozt" jazz? 0% M n/0Z6 PatentedSept. 25,1945

HEAT SHIELD FOR INCANDESCENT LAMPS Louis A. McNabb, Glenview, 111.,assignor to The Bell 8; Howell Company, Chicago, 111., a corporation ofIllinois Application October 29, 1942, Serial No. 463,845

' 2 Claims.

My invention relates to a heat shield device of a character especiallysuitable for use about relative small high wattage lamps as in motionpic this . is highly absorbent of heat radiated from the incandescentfilament of an enclosed lamp and which defines passages for the guidanceof an air stream to conduct away the absorbed and radiatedheat.

A further object is the provision of a device according to the precedingobject, economically fabricated into a unit conveniently insertable intothe ventilated lamp chamber of a light beam proiecting apparatus.

With these objects in view my invention consists in certain features ofnovelty in the construction, combination, and arrangement of parts bywhich the said objects and other objects, hereinafter appearing, areeffected all as fully described with reference to the accompanyingdrawings, and more particularly pointed out in the appended claims.

In the drawings:

Fig. 1 is a vertical sectional view taken centrally through the lampchamber portion of a motion picture projector housing and likewisethrough a preferred embodiment of the invention installed therein;

Fig. 2 is a. plan view of the heat'shield device shown in Fig. 1, therebeing also shown a fragmentary portion of-the projectorhousing, the viewbeing taken as indicated on the line 22 of Fig. 1;

Fig. 3 is a horizontal sectional view taken on the line 3-3 of Fig. 1;

Fig. 4 is a fragmentary front'elevational view oi the lamp chamber,illustrating flat surface areas for facilitating the assembly therewithof film-advancing mechanism and a ventilating fan casing, the view beingtaken on the line 4--4 of Fig.

Fig. 5 is a fragmentary vertical sectional view of a portion of the heatshield structure, taken on the line 5-5 of Fig. 2;

Fig. 6 is a fragmentary vertical sectional view of a different portionof the heat shield structure, taken on the line 8-6 of Fig. 3;

Fig. '7 is a view taken in elevation of the entire heat shieldstructure, with the outer shell thereof shown in section tae'xposeinterior parts in side elevation; y"

Fig. 8 is a side elevational view of the entire heat shield structure;

Fig. 9 is an enlarged fragmentary view illustratlng fastening means forfabricating heat shield rings onto the lower end of the inner shell ofthe heat shield structure; and

Fig. 10 is a plan view of one of said rings which has centering studsspaced circumferentialh' about its outer periphery.

With continued reference to the drawings, and particularly to Figs. 1 to4, there will be seen a lamp chamber 20 comprising but part of a motionpicture projector'hou'sing 2|. This lamp chamber has a substantiallycylindrical upright side wall 22 circumscribed exteriorly byaxially-spaced cooling fins 23 distributed along its entire length andreinforced by any desired number of vertical ribs R of which one isshown in Figs. 1 and 3. Said chamber is open at both its top and bottomends. Diametrically opposite openings 24 and 25 respectively in the backand front of the .chamber side wall are for the accommodation of a lightreflector unit 26 and a light condensing lens unit 21.

Th reflector unit includes a plug 28 of which a threaded portion ismeshable with threads within the opening 24 whereby this plug and areflector member 29 attached thereto by a frame 30 are removablyassociated with the lamp chamber.

The lens unit 21, as noted in Fig. 4, is mounted in a frame 3| which isslidably carried upon horizontal vertically spaced guideways 32 and 33,making possible lateral removal and insertion of the lens unit.

An electric motor housing H, cast integrally with the lamp chamber 20,presents its front end in a common plane with front flat surface areas38 and 31 bordering the upper and lower sides of the generallyrectangular chamber opening 25, so that a fan housing 38, Fig. 2, and anair passage (not shown) leading therefrom can be conveniently assembledin communicative relation with and sealed relation .about said chamberopening. In Fig. 4 it can be seen that the front face of thelens-carrying frame is flat to enable it to have a sealing sliding fitwith a contiguous back face portion 39, Fig. 2, of the fan housing 38 sothe seal between said housing and the lamp chamber about the opening 25does not interfere with movement of said frame. Also it will be notedthat the frame 3| has a rectangular openling 40 within the opening 25and through which a portion of the air can pass from the fan housing 38into the lamp chamber, that part of the opening 25 below and to theright, Fig. 4, of the sleeve-like and concentric.

lens unit 21 conducting the greater part of the air into the lampchamber. An upwardly procircular hole 61 is formed in the back wall ofthe -tubular member 66 whereas a straight edged jbcting portion 4| ofthe opening 25 is shown in Figs. 3 and 4.

A relatively small high wattage lamp 42 having a glassenvelope 43 and abase portion 44 is supported by the latter upon and within acurrentsupplying socket structure 45 at such an elevation that theincandescent filament 46 is disposed coaxially with the reflector 29 andthe condensing lens unit 21. This lamp socket structure comprises acylindrical insulator shell 41 arleads from an electrical energy source.Ring 48 protrudes radially inwardly from the inner periphery of theshell so it is engageable by and can serve as an axial abutment for anelectrical conductor annulus A hole 52 in the annulus receives the lampbase while lugs 53 upon a downtumed cylindrical flange 54 about thishole are solder-connected as at 55 to the lamp base to establish a goodelectrical connection therewith and to prevent relative movementbetweenthese parts both axially and rotatively.- The annulus 5| has a lug 56bent upwardly from its outer edge. Therefore, when this annulus 5| abutsthe ring 48 the lamp will be at the proper height to align its filamentwith the reflector 29 and with the lens unit 21, and when said upturnedlug 56 is engaged in a notch 51 therefor in the ring 48 the lamp will beangularly positioned with the plane of the filament 46 thereof normal tothe common axis of the reflector 29 and the condensing lens unit'21. f

The inner-periphery of the conductor ring 49 is threaded for receivingthe threaded portion 58a of a closure plug 59 for the bottom of theshell 41. A milled finger grip portion 60 of this plug facilitatesengagement thereof for screwing the sameinto the ring .49. The threadedportion 580 of the plug 59 is of metal or other electrical conductormaterial and-is'connected electrically by means (not shown)"" with aspring contact member 6| anchored within the plug and having a contactbutton 62 arranged coaxially therewith for pressing against the centralelectrode member 63 of the lamp. Thus it will be seen that when the plug59 is screwed into the ring 49 the spring 6| and the button 83 thereon,in addition to mak ing electrical contact with the electrode 59, will toits limit determined by abutment of the annulus 5| with the ring 48.

Sufficient clearance is provided by the lamp chamber radially of thelamp to provide ample space for the heat shield assembly now to bedescribed. This assembly which is of a unitary structure as shown inFigs. 7 and B is generally designated 65. Such assembly consists of aplurality of coaxial circular parts of which some are An outercylindrical A generally notch 68 is formed in the lower front wall ofsaid member, this notch having an upper edge 69 extendingperpendicularly to the axial elements of the tubular member and straightvertical edges as extending from the ends of the edge 69 and downwardlyto the lower end of said member.

'In Fig. 1 it will be seen that the-back wall open- "ranged coaxiallywith and below the lamp chamber.

ing 61 is for accommodating the reflector mem- 'ber 29 and that theopening 68 is for accommodating the lens unit 21. Two diametricallyopposite ears 1| and 12 are cut from the upper end of the tube 66 andbent perpendicularly to the tube side walls. These ears 1| and 12 areprovided with end notches 13 and 14 for registering.

with threaded recesses 15 and 16 within the upper end of the lampchamber 20. Prior --to assembly of the reflector unit 26 and of the lensunit 21 with the lamp chamber 28 the heat shield unit 65 will beinserted downwardly into the .chamber, bringing the notches 13 and 14into the aforesaid registry with the threaded recesses 15 and 16, theears 1| and 12 then resting upon the upper end of the lamp chamber forsupporting the heat shield unit. Subsequently a ring 11 is laid in placeabove the chamber wall and onto the ears 1| and 12, thereby bringingholes 18 of the ring into registry with the threaded recesses 15 and 19so that machine screws 19 can be in-- serted through these holes androtated into threaded relation with the recesses 15 and 16 asillustrated in Fig. 1 for fixing the ring and the heat shield device inassembly with the lamp chamber. It will also be seen that the ears 1|and 12 together with the machine screws 19 provide means for centeringthe upper end of the shield unit in the lamp chamber, and the lower endof the unit is centered in said chamber by a plurality ofcircumferentially spaced tab-like parts 88 formed integrally with thelower end of the tubular member 66 and projecting radially outwardlytherefrom. These members 88 engage the inner periphery of the lampchamber as illustrated in Figs. 1 and 3.

A frusto conical member 8| depends from the lower end of the tube 66 bymeans of four integral lugs 82 projecting upwardly fromcircumferentially spaced positions about its upper edge and into contactwith respective inner peripheral portions .of said tube. A firmconnection between the lugs 82 and the tube 66 may be effected by spotwelding as indicated at 83 in Fig. 8. A

notch84 is formed in the lower edge of the member 8| and providesclearance for the lug 56, Fig. 1, which is electrically connected withthe source of electrical energy for energizing the lamp. Displacement ofthe member 8| axially from the tube 66 is so chosen that a space S willobtain between this member 8| and a heat conducting liner 86 within theflared upper end of the shell 41. This construction provides for thecirculation of air downwardly into the shell 41 for keeping the base ofthe lamp at an operating temperature lower than would exist if suchventilation were not provided, thereby preventing deterioration of thelamp base.

A second tubular member, 81, also cylindrical, is disposed within thetubular member 66. This member 81 is shorter than the member 66 but isso arranged axially thereof that openings 88 and 89 within the back andfront walls thereof register with the openings 61 and 68 of the outertubular member 66. The back wall opennig 88 is circular and of adiameter for receiving the of ve'rtically extending and 95, best shownin Figs. 3 and 9, are formed upon the inner periphery of 'the tube 81.In the reflector member 29 as illustrated in Fig. 1, whereas the opening89 has one vertical straight edge 90, a curved opposed and generallyvertical edge 9I and two horizontal upper and lower edges 92 and 93; seeFigsk'luand 8. .This opening 89receives the inner end of the 'lens unit21. '.'A series light reflecting facets 94 -'cated in axially spacedrelation by means of spac- -'e'r sleeves I04 upon headed pins I05 spacedcirpresent structure thesefacets are formed by corrugating the metalsheet from which the sleeve 81 is fabricated with the corrugationsthereof ex-' tending longitudinally-of the sleeve to provide the sleevewith internal and external longitudinally extending fluted surfaces,opposite edge portions 96 and 91 of the sheet being overlapped andwelded together at points W, Fig. 7, in the fabrication-of the tube.Support of the tube 81 cenv trally within the tube 65 is accomplished inpart" by lugs 98 which are struck radially outwardly fromcircumferentially spaced upper end portions of the tube 81. Each ofthese lugs includes a narrow end portion 99 which projects through arespective hole I00 therefor in the tube 66.

Shoulders IOI on the lugs 90 are adapted to abut against the innerperiphery of the tube 56 for holding the tube 81 centered with respectto said 81 more distantly downwardly than illustrated in Fig. 1, a gridarrangement I02 consisting of a plurality of flat rings I03 and a ringI03a fabricumferentially thereof, is attached to the lower end of thetube. These rings I03 and I03a have substantially the same outsidediameter as the tube 81 and such grid arrangement is attached to thelower end of the tube by either a soldered or welded connection (notshown) between the tube and upper end portions of the pins I05 which areinserted impingedly thereagainst. Slippage tube 66 while the narrow endportions 99 prevent relative axial displacement of the tubes 86 and 81.This detail is shown in Fig. 6.

The inner tubular member 81 is designed for absorbing the heat radiatedfrom the lamp filament 46 and for having the heat thus absorbedconducted away therefrom by an air current directed into the lampchamber through the opening 25 and passed upwardly through the chamher.In Fig. 1 it will be noted that the plaited or faceted tube 81 registerswith the filament 46 at a portion of said tubular member generallymidway between its ends. Most of the heat radiated from the filament 45emanates radially of the lamp and therefore strikes the tube 81, andbecause of the angular arrangement of the facets 94 and 95 with respectto these radially directed rays, said rays will not be reflecteddirectly back toward the lamp but instead will be deflected toward thefacet 94 or 95 opposite to the facet 95 or 94 to that first struck byany direct ray. As a consequencethe direct rays from the filament aremore efficiently absorbed by the tube 81, the heat reflected back to thelamp being practically only by re-reflection with resulting minimizationthereof. Moreover the formation of the facets 94 and 95 by corrugatingthe tube wall provides more material in this wall which correspondinglyincreases its heat absorption capacity, and the external fluted surfaceformation of the tube resulting from corrugating the tube wall providesa plurality of different external surfaces respectively disposed to forman extended external radiating surface formation. Heat absorbed by thistube wall is conducted away from it at both its inner and outerperipheries by the aforesaid air stream passing upwardly through thelamp chamber.

While most of the heat radiating from'the fllament 46 is directedradially of the lamp, some of the heat will radiate downwardly into thatarea exteriorly of the envelope 43 adjacently below the tube 81. If thisdownwardly and outwardly radiated heat should strike the verticalplaited wall 81, part of it would be deflected radially inwardly anddownwardly from the point of impingement with the tube inner periphery.causing this deflected heat to impinge upon the inner of the rings I03and I03a and their spacer sleeves from the unheaded shanks of the pinsI05 is precluded by swaging the pin shanks as indicated at I06 in Fig.9. The only difference between the rings I03 and the ring I03a is thatthe latter has a number of circumferentially spaced lugs I01, Figs. '1and 10, for engaging the inner periphery of the outer tube 86 forcooperating with the shoulders IOI on the lugs 98, Figs, 6 and 'I, formaintaining the axial alignment of the tube 81 and of the grid structureI02 with the outer tube 86.

Now upon referring to Fig. 1 it can be seen that heat radiateddownwardly and outwardly from the filament 46 into the circular zoneoccupied by the grid structure I02 will for the most part impinge uponthe upper flat faces of the rings I09 and I03a, and since the angle ofreflection of this radiated heat is equal to the angle of incidence, theheat reflected from these upper flat surfaces of the rings I03 and I03awill be in a direction radially outwardly and upwardly from the ringsinto the annular space between the grid structure and the outer tube 66.Likewise heat radiated from the filament 46 downwardly into impingementwith the lower portion of the tube 81 and which is not absorbed by thattube will be deflected downwardly and generally diametrically across thetube into the grid structure, and that part of these deflected raysstriking the flat upper surfaces of the grid rings I03 and I03a will beagain deflected, into said annular space between the grid structure andthe outer tube 66.

Radiant heat emanating from the filament 46 and finding its way axiallydownwardly of the tube more distantly than the grid structure I02 willimpinge upon the frusto conical member 8I which will diffuse these heatrays, deflecting most of them striking any inner peripheral portionthereof generally diametrically oppositely from such portion andupwardly into that annular zone of the lamp chamber between the gridstructure I02 and the upper end of the frusto conical member 8|. Thiswill bea relatively small portion of the radiant heat generated in thelamp fliament and when absorbed by the chamber walls is readilydissipated therefrom both exteriorly and by the air current directedupwardly through the chamber. Such heat as reaches the upper interiorportion of the shell 41 by radiation and convection will be mostlyabsorbed b the metal liner 86 and conducted by this liner to the metalside wall of the lamp chamber against the lower sorption and conductionfor dissipating the heat ber.

to preclude that heat reaching the lamp base.

A guard and light shield structure I08 is fitted into the upper end ofthe sleeve 66 spacedly above the inner sleeve 81. This grid structureI08 comprises three concentric cylindrical members I09, H and III ofsuch graduated diameterthat annular spaces are provided therebetween.Two

/ cross plates H2 and H3 arranged in respective vertical planesintersecting at right angles are interfabricated with the cylindricalmembers I", I In and III for holding them in assembly. The lowermostcross plate H3 has end projections H3a similar to those indicated at H2aat the opposite ends of the cross plate H2 excepting that theprojections at the ends of the plate III are adjacently to its upperedge whereas the projections at the ends of the plate H2 are ad-Jacently to its lower edge, and in assembling this grid member these endprojections of the plates H2 and H3 are inserted into respective holesH5 disposed diametrically oppositely in the outer cylindrical memberIII, see Fig. 7. In the assembly of the cylindrical members I09 and H0with the cross plates H2 and H3 diametrically opposite notches II 6 inthese cylindrical members-engage downwardly about the cross plate I I3and diametrically opposite notches III of these cylindrical membersengage upwardly about diametrically opposite notched portions H8 of thecross plate H2.

It will be observed that the lower end of the outer cylindrical memberIII of the guard and light shield assembly I08 is flared and thatcircumferentially spaced and paired notches I20 are formed in thisflared portion of the sleeve communicatively with its lower edge todefine respectively associated bosses I2I therebetween. Each of thesebosses is formed with a bendable tongue I22, When the grid structure I08is inserted ax-.

ially into the tube 66, flared end of the outer sleeve III foremost, thetongues I22 will be respectively circumferentially aligned with holesI23 in the tube 68 so that upon these tongues arriving in axial registrywith said holes I23 they can be thrust outwardly therethrough and bentupwardly as illustrated in Figs. 5 and 8. This operation completes theassembly of the heat shield device.

It is after this complete assembly of the heat shield unit as shown inFigs. 7 and 8 that such unit is slid downwardly into the lamp chamberpreparatory to the securement thereto by the ring I1 and screws I9 asexplained hereinabove, and, obviously, this insertion of the unit intothe lamp chamber is done prior to assembly of the reflector unit 28 andthe lens unit 21 with said chamber so the latter units will not obstructdownward movement of the shield unit into said cham- In the operation ofthe device, air is forced into the lamp chamber by a fan (not shown) inthe housing 38 and which fan is driven by a projector operating motor inthe motor housing H. This air from said fan enters the lamp chamberthrough the opening 25. Part of the air is circulated downwardly intothe lamp socket or shell 41 about the lamp base 44 to conduct heattherefrom and from the annulus member 5|, the liner 86 and the frustoconical member 8|. Part of the air is directed between the grille ringsI03 and Mia to conduct heat from the grille I02. One component of theair stream passes upwardly between the lamp envelope 43 and thecorrugated tube-81 while another component passes emanating in theirdirection from the filament 46 upwardly between said tube 81 and'thetube 68 and still a third component passes upwardly between the tube 66and the lamp chamber side walls since the ears ll and I2 at the top ofthe tube 66 do not obstruct the annular space between such tube and saidchamber wall. Therefore the air which absorbs heat from the variousheat-absorbing parts within the lamp chamber is elevated from the lampbase and ultimately discharged through the guard and light shieldstructure I08 wherefore said base is subjected to a relatively coolportion of the air stream.

Much of the radiant heat absorbed by the corrugated tubular member, inthe very effective manner hereinabove explained, is conducted outwardlythrough the upper end opening of the cas. ing by the air streamcomponents passing upwardly along its inner and outer peripheries, andbecause of the shielding effect of the outer tube 68 and the air streamcomponent between it and the lamp chamber wall the latter will notexceed a temperature atwhich it can be touched with the unprotectedhands of an operator without discomfort.

While I have thus described my invention, I do not wish to be limited tothe precise details described, as changes may be readily made withoutdeparting from the spirit of my invention, but having thus described myinvention, I claim as new and desire to secure bylLetters Patent thefollowing:

1. A generally tubular heat absorbing and dissipating shield forspacediy enclosing an incandescent electric lamp in generally coaxialrelation therewith and having a portion including the lamp filamentopposing region thereof of plaited form providing internal and externallongitudinally extending fluted surface formations of which the internalsurface formation provides a plurality of different surfaces extendinglongitudinally of the lamp and respectively disposed at acute angles toheat rays impinging thereon from the lamp filament to reflect theunabsorbed portion of these heat rays in paths not traversing the lampand on to others of said surfaces and of which the external surfaceformation provides an extended heat radiating surface formation, andhaving a second portion adjoining the lamp base adjacent end of saidfirst mentioned portion and comprising a plurality of air passageproviding-slats spaced longitudinally of and extendin angularly aboutthe lamp and providing surfaces facing generally in the direction of thelamp filament and disposed at acute angles to heat rays impingingthereon from the lamp filament to reflect the unabsorbed portion ofthese heat rays in paths radially outward from the lamp.

2. In a device of the character described, the combination of anelongated outer enclosure adapted to have an incandescent electric lamplocated in central longitudinally extending relation therein andprovided with air inlet and outlet openings respectively disposed forthe passage of an air current through the enclosure from the region ofthe base of the lamp to the top of the lamp, of a generally tubular heatabsorbing and dissipating shield located. in and extendinglongitudinally of said enclosure in surrounding relation with the lampand spacediy related with said enclosure and lamp to provide airpassages interiorly and exteriorly of said heat shield, and said heatshield having a, portion including the lamp filament opposing portionaaeaoae thereof of plaited form providing internal and externallongitudinally extending fluted surface formations of which the internalsurface formation provides a plurality of different surfaces extendinglongitudinally of the lamp and respectively disposed at acute angles toheat rays impinging thereon from the lamp filament to reflect theunabsorbed portion of these heat rays in paths not traversing the lampand onto others of said surfaces and of which the external surfaceformation provides an extended heat radiating surface formation, andsaid heat shield having a second portion adjoining said first mentionedportion in the region of the lamp base and comprising a plurality of airpassage providing slats spaced longitudinally of and extending angularlyabout the lamp and providing surfaces facing generally in the directionof the lamp filamerit and disposed at acute angles to heat raysimpinging thereon from the lamp filament to reflect the unabsorbedportion of these heat rays in paths radially outward from the lamp.

LOUIS A. MCNABB.

